Ink jet printer with a nozzle covering and cleaning device

ABSTRACT

A description is given of an ink jet printer having an ink jet print head which can be displaced parallel to a print line, and a print backing support used to support a recording medium, a covering device and a cleaning device for the ink nozzles of the ink jet print head. The covering device, the cleaning device and a supporting section for the recording medium are arranged on a rotatable disk within the printing area of the ink jet print head.

BACKGROUND OF THE INVENTION

The invention relates to an ink jet printer with a covering and cleaningdevice for the ink nozzles of an ink jet print head, which covering andcleaning device are mounted on a segment of a periphery of a disk, whichis arranged in the area of the ink jet printer and which rotates on anaxis extending through a circle.

An ink jet printer with a covering and cleaning device for the inknozzles of an ink jet print head is disclosed by DE-C-36 11 666.Described in this document is an ink jet print head which can bedisplayed parallel to a print line and a roll-like print backing supportused to support a recording medium opposite the ink jet print head andaligned parallel to the print line. Arranged alongside the printingarea, that is to say the maximum area which can be assumed by therecording medium and the maximum area which can be printed by the inkjet print head, is a parking area having a covering device and acleaning device for the ink nozzles of the ink jet print head.

As a result of the parking area, the printer obtains a width whichcannot be accepted in many applications. This applies in particular tocashdesk printers of the type as described, for example, in the Germanpatent application 197 09 941.6. Such cashdesk printers are ofteninstalled in a cutout in a cashdesk, so that for their outline aquasi-standard has been formed, having a width dimension which is onlyslightly greater than the width of the largest document to be printedwith the printer. This document is in DIN A4 format, that is to say hasa width of 210 mm. In printers of this class, the ink jet printingprinciple has therefore not been used hitherto.

It has already been proposed, in U.S. Pat. No. 5,051,761, to fit thecovering device and the cleaning device on the periphery of a circularor circular-segment-like disk arranged in the printing area of the inkjet print head, and it is possible for the disk to rotate about an axisextending through the center of the circle. In this case, the recordingmedium is supported in the printing area by an endless transport belt,which is stretched out between two deflection rollers. One of thesetransport rollers—as viewed in the transport direction of the recordingmedium—is arranged upstream of the printing area and the other isarranged downstream of the latter. Cut out of the transport belt is awindow, through which the covering device or the cleaning device act onthe ink jet print head if the disk is lifted in the direction of theprinting area. The arrangement comprising transport belt and deflectionrollers is complicated and needs a relatively great amount of space.Added to this is the fact that the transport belt firstly has to bebrought into a specific peripheral position relative to the ink jetprint head before the covering device or the cleaning device can act onthe ink jet print head. This requires additional monitoring devices andcontrol measures for positioning the transport belt, and makes theprinter slower, since the recording medium must have left the transportbelt before the window can be brought into the area of the ink jet printhead.

SUMMARY OF THE INVENTION

The object of the invention is to provide an ink jet printer having acovering and cleaning device arranged in the printing area of the inkjet print head for the ink nozzles of the ink jet print head, and topropose a supporting device, for a recording medium, which can bebrought into the printing area instead of the covering and cleaningdevice.

The object is achieved by an improvement which is that a disk with thecovering device and the cleaning device in position in a gap between twoparts of a print backing support, and has a supporting section for therecording medium arranged on a segment of the periphery which can berotated into position during printing.

The covering device and the cleaning device are arranged in the printingarea of the ink jet print head. The fact that the covering device, thecleaning device and the supporting section for the recording medium arearranged on the periphery of a circular or circular-segment-like diskwhich can be rotated about an axis extending through the center of thecircle, means that no additional space is needed for a parking areaoutside the printing area or upstream and downstream of the ink jetprint head. The disk can be arranged in the printing area anywherewithin the print line. As a result of the rotation of the disk about itsaxis, the covering device can be brought in front of the nozzle plate ofthe ink jet print head, the cleaning device can be moved past the nozzleplate, or the supporting section can be pivoted into the printing area.Since the covering device must in any case be pivoted away in front ofthe nozzle plate before a printing operation, the supporting section canbe brought into the printing area without additional effort by simplyrotating the disk further.

The axis can be aligned either parallel to the print backing support orperpendicular thereto and parallel to the plane of the recording medium.

The disk is preferably rotated by a motor, in particular a steppingmotor. In the latter case, the angular position of the disk can be fixedsimply by counting the motor stepping pulses. The drive to the disk ispreferably provided via a toothing system, at least on part of itsperiphery, which meshes with a gear wheel driven by the motor.

In a preferred development of the invention, the disk can be displacedalong the print backing support. As a result, in the case of a cashdeskprinter having a receipt printing station, such as is disclosed by theGerman patent application 197 09 941.6, the disk can be displaced intothe part of the printing area which is not occupied by the receipt paperstrip. If a receipt printing station and a journal printing station areused alongside each other, the disk can be brought into the gap betweenthe receipt paper strip and the journal paper strip.

In order to ensure that the covering device is lifted perpendicularlyoff the nozzle plate of the ink jet print head, the covering device isconnected to the disk via a radially adjustable slider, and fixed to theslider is a control pin which is guided in a snail-shaped or spiralcontrol curve arranged in the ink jet printer and surrounding the axis.The control curve is formed on a control plate which is held on the axisand is stationary with respect to the disk, that is to say does notrotate together with the disk.

Further features and advantages of the invention emerge from thefollowing description which, in conjunction with the appended drawings,explain the invention using exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first exemplary embodiment of an ink jet printer in aschematic, perspective front view,

FIG. 2 shows a schematic side view of the ink jet printer illustrated inFIG. 1,

FIG. 3 shows a second exemplary embodiment of an ink jet printer in aschematic plan view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated in FIG. 1 is a first exemplary embodiment of an ink jetprinter 10 in a schematic, perspective front view, in which all theparts of the printer which are not relevant to the invention have beenleft out. In the figure, one side wall of a printer frame is designatedby 12. A bar-like print backing support 14 projects, perpendicular tothe surface, from that side of the side wall 12 that points toward theinterior of the printer. This print backing support is divided by a gap16 in the central area of the ink jet printer into two parts 14′, 14″.The print backing support 14 is formed on a paper guide surface 38 (FIG.2). An ink jet print head 18 is mounted such that it can be displacedalong the print backing support 14 and parallel to the latter in thedirection of a double arrow A, forming a print line.

In the gap 16, a cylindrical disk 20 is mounted such that it can rotateabout an axis 22, which coincides with the axis of the cylinder. Theaxis 22 extends parallel to the print backing support 14 and on its sidefacing away from the ink jet print head 18. Arranged on the periphery ofthe disk 20, in each case offset at an angle from one another, are acovering device 24, a cleaning device 26 and a supporting section 28.The covering device 24 has the form of a cap that is open with respectto the nozzle plate of the ink jet print head 18 and consists of aresiliently deformable, ink-resistant plastic or rubber. The cleaningdevice 26 has the shape of a plate which projects radially from theperipheral surface of the disk 20 and is aligned axially. It is likewiseformed from a resiliently deformable, ink-resistant plastic or rubber.The supporting section 28 is a section of enlarged disk diameter. Itextends over the entire width of the disk 20. If the latter is rotatedin such a way that the supporting section 28 is opposite the ink jetprint head 18, the surface of the supporting section 28 is flush withthe print backing support 14.

The disk 20 can be displaced within the gap 16 in the direction of adouble arrow B, between the positions 20′ (illustrated with continuouslines) and 20″ (drawn dashed). In the position 20″, the disk 20 isillustrated in an angular position in which the covering device 24 facesthe ink jet print head 18. In this angular position, the cap-like shapeof the covering device 24 can be seen. The fact that the disk 20 can bedisplaced makes it possible to use receipt paper strips 30 or journalpaper strips 32 of different widths. The setting of the disk 20 whenprinting a counterfoil 34 which extends over the gap 16 will bedescribed further below.

FIG. 2 shows a schematic side view of the ink jet printer 10 illustratedin FIG. 1. The disk 20 is mounted on a coaxial shaft 36. In addition, inits peripheral area facing away from the paper guiding surface 38, it isprovided with a toothing system 40, which meshes with a gear wheel 44that can be driven by a stepping motor 42.

The covering device 24 is arranged at one end of a slider 46 which canbe adjusted radially in relation to the disk 20 and which can be rotatedtogether with the disk 20. Fastened to the slider 46 is a control pin48, which is aligned parallel to the shaft 36 and is guided in a spiralshaped groove forming a snail-like control curve 50 which surrounds theaxis 22. This control curve or cam surfaced is in turn formed on acontrol plate 52 which is held on the axis 22 and is stationary withrespect to the disk 20, that is to say does not rotate together with thelatter. In the region of the shaft 36, the slider 46 is provided with aslot 54, with which it is mounted on the shaft 36 such that it can bedisplaced longitudinally.

If the disk 20 is rotated in the counterclockwise direction, the controlpin 48 runs along in the control curve 50. In the process, the slider 46is displaced radially in the direction of the axis 22, so that thecovering device 24 is lifted off the nozzle plate of the ink jet printhead 18 and is pivoted away upward in front of the latter. If the disk20 is rotated further, the cleaning device 26 comes into the area of theink jet print head 18. In the process, it is deflected resiliently, sothat its leading edge 56, aligned parallel to the axis 22, sweeps overthe nozzle plate of the ink jet print head 18 and in so doing wipes offcontaminants adhering to the latter. The cleaning action can beincreased further by rotating the disk 20 to and fro many times. For thepurpose of printing, the disk 20 is rotated further until the supportingsection 28 is opposite the printing area 18. The latter can then bedisplaced in the print line direction over the entire printing area.

If a counterfoil 34 which extends over the gap 16 is to be printed, thedisk 20 is controlled in the following way, starting from the positionillustrated in FIG. 2, in which the printing area 18 is covered: theleading edge of a document 34 fed to the ink jet printer 10 in thedirection of the arrow C is detected by a first light barrier 58arranged upstream of the print backing support 14, whereupon a documenttransport device (not illustrated) is stopped. The disk 20 is thenrotated as described above until the supporting section 28 is oppositethe ink jet print head 18. As a result, the gap 16 is largely closed, sothat the document 34 is also supported in this area. The fact ofreaching this position is determined using the number of pulses suppliedto the stepping motor 42, and the document transport device is thereforeenabled. Following the printing of the document 34, the latter istransported out of the ink jet printer 10 either in or counter to thedirection of the arrow C. The document 34 has certainly left the ink jetprinter 10 when neither the first light barrier 58 nor a second lightbarrier 60 arranged above the print backing support 14 reports thepresence of a document. The disk 20 is then rotated back in theclockwise direction into the position in which the covering device 24covers the nozzle plate of the ink jet print head 18, which is againdetermined using the number of pulses supplied to the stepping motor 42.

FIG. 3 shows a second exemplary embodiment of an ink jet printer 100 ina schematic plan view. This differs from the ink jet printer 10illustrated in FIGS. 1 and 2 in the fact that the axis 122 and thereforethe shaft 136 of the disk 120 are aligned perpendicular to the printbacking support 114′, 114″ and parallel to the plane of a recordingmedium 134. The disk 120 is shown in its position ready to print, butotherwise the arrangement is identical to that shown in FIG. 2.Identical positions are therefore identified by identical referencesymbols.

I claim:
 1. An ink jet printer having an ink jet print head with inknozzles, said print head being displaceable parallel to a print line,and a print backing support used to support a recording mediumpositioned opposite the ink jet print head and aligned parallel to theprint line, a covering device and a cleaning device for the ink nozzlesof the ink jet head, the covering device and cleaning device beingarranged on a portion of a periphery of a disk having at least the shapeof a circular segment, said disk being rotatable about an axis extendingthrough the center of said circular segment, the print backing supportbeing divided by a gap into two parts, the disk being located in the gapand having a supporting section for the recording medium being arrangedon the periphery of the disk.
 2. An ink jet printer according to claim1, wherein the axis of the disk is aligned parallel to the print backingsupport and parallel to the recording medium.
 3. An ink jet printeraccording to claim 1, wherein the axis of the disk is alignedperpendicular to the print backing support and parallel to the plane ofthe recording medium.
 4. An ink jet printer according to claim 1,wherein the disk can be rotated by a motor.
 5. An ink jet printeraccording to claim 4, wherein the motor is a stepping motor.
 6. An inkjet printer according to claim 4, wherein the disk has a toothing systemon at least a part of its periphery, which meshes with a gear wheeldriven by said motor.
 7. An ink jet printer according to claim 1,wherein the disk can be displaced along the print backing support.
 8. Anink jet printer according to claim 1, wherein the covering device isconnected to the disk by a radially adjustable slider, said slider beingfixed to a control pin which is guided in a spiral-shaped control groovewhich surrounds the axis and is formed on a contact plate which is heldon the axis and is stationary with respect to the disk.
 9. An ink jetprinter according to claim 1, wherein the covering device is cap-like.10. An ink jet printer according to claim 1, wherein the cleaning deviceis plate-like and of a resilient deformable material and projectsradially from a peripheral surface of the disk.
 11. An ink jet printeraccording to claim 1, wherein the cleaning device is arranged betweenthe covering device and the supporting section.